Method and apparatus for the high speed production of magnetic films



1968 J. M. AMARO ET 3,362,893

. METHOD AND APPARATUS FOR TH G FEED PRODUCTION OF MAGNETIC FILM FiledApril 27, 1964 2 Sheets-Sheet l FIG.1

' INVENTORS ATTORNEY ET AL 3,362,893

THE] HIGH SPEED J. AMARO METHOD AND FOR PRODUCTION OF MAGNETIC FILMSARATUS Jan. 9, 1968 2 Sheets-Sheet 2 Filed April 27, 1964 United StatesPatent METHOD AND APPARATUS FOR THE HIGH SPEED PRGDUCTION OF MAGNETICFILMS Jack M. Amara, N ewhurgh, and Kenneth F. Greene, Wappingers Falls,N.Y., assignors to International Business Machines Corporation, NewYork, N .Y., a corporation of New York Filed Apr. 27, 1964, Ser. No.363,342 14 Claims. (Cl. 204-15) This invention relates to methods andapparatuses for the deposition of a layer of metal onto the surface of aresistive article. The invention is more particularly concerned withtechniques for electrodepositing at high speeds a metal layer havinguniform magnetic properties onto one side of a resistive article.

The electrodeposition of a metallic coating onto an article which isresistive presents problems which are not present in theelectrodeposition onto conductive metal articles. A typical article ofthis resistive class would include a substantially dielectric ornonconductive portion having thereover a thin film of conductive metal.The metallic coating is so thin that it is effectively resistive to thepassage of an electric current in comparison to an all-metallic articleof the same metal. When the resistive article is connected as thecathode of an electroplating cell, the electroplating current densitywill rapidly decrease from a peak current density at the power source toa value less than limiting current density of the metal ion to beelectroplated due to the resistive nature of the thin metal coating.

The current carrying capacity of the conductive film on the surface ofthe resistive article is limited by the resistive heating of theresistive article. Resistive heating causes a degradation of thedielectric substance, par ticularly when the dielectric substrate iscomposed of a plastic material such as polyethylene terephthalate. Theresistive heating also can cause a poor electrodeposit.

Prior art methods and apparatuses for electrodepositing a metallic filmonto a high resistive article used exclusively cathodic contactsexternal to the electroplating bath. A difficulty encountered with theseprior art apparatuses and methods is that the external contact producesa nonuniform current density distribution upon the resistive work piece.The current density distribution goes from a high value at theelectroplating surface to a value where no significant electrodepositioncan be accomplished in only a few centimeters below the bath surface.Therefore, in the case of an elongated, continuously moving article,there is no electrodeposit being applied to the surface of the workpiece during most of the resistive articles path through theelectroplating bath. To increase the amount of electrodeposit the speedat which the continuously moving resistive article is moved through thebath is maintained at a low value. In this way the time in which thearticle is in the region of significant current density is increased.However, to obtain sufiicient thicknesses of electrodeposit, a series ofelectroplating stages is required through which the resistive article tobe electroplated is passed.

An electrodeposit of a magnetic coating onto a resistive article furthercomplicates the already diflicult problem. It is, however, particlularlydesirable to be able to apply a thin magnetic electrodeposit to a longlength of high resistive web composed, for example, of a thermoplasticbase having a thin metallic coating. Such a structure could provide asuperior magnetic recording tape. The tape would have an extremely lowinertia and be flexible enough to travel at high speeds around hearingmembers such as capstans or the like. The thin magnetic layer issufliciently thin to insure recording densities and magnetic propertiessubstantially superior to the ice present day magnetic oxide tapes. Ahighly conductive metallic web cannot be successfully used as a supportfor the magnetic layer in a magnetic recording tape because such a weblacks the required low inertia and high flexibility properties. Thealternate support then is a flexible thermoplastic web having aconductive coating on its surfaces. This initial conductive film on thethermoplastic web is very thin. The thicker this film is, the greaterwill be the inertia of the tape, and if made too thick it will bebrittle and tend to crack. However, the thinner the film is the moreresistive it is to the current flow and the more nonuniform will be theelectroplating current densities where, as in the prior art, an externalcathodic contact is used.

The control of the crystal size of the deposited magnetic metal isnecessary to produce a magnetic recording tape having acceptablemagnetic properties. The crystal size in the electrodeposit is importantbecause the important magnetic properties of the tape, such ascoercivity, are dependent thereon. The coercivity of the magnetic layer,for example, increases as the electrodeposits crystal size decreases.Unfortunately, the electrodeposits crystal size is dependent upon thecurrent density. Because increased current density decreases theelectrodeposits crystal size, control and uniformity of the currentdensity are again prime requirements. Using the prior art externalcathodic contacts the current density distribution on the conductivefilm of the resistive web cannot be successfully controlled. Therefore,the magnetic properties of the electrodeposit are, in turn, difficult tocontrol.

The prior art apparatuses necessarily produce magnetic layers on bothsides of the resistive web. When the magnetic recording tape is used,only one side of the tape is used for recording of information. Theother side of the recording tape is the surface which contacts alldriving means. Therefore, there is no reason to apply a magnetic coatingto more than one side of the resistive web. Further, it has been foundthat the magnetic coating on the back side of the magnetic tape in factis detrimental. Over periods of time, this magnetic layer tends to weardue to its constant contact with the driving means in the start-and-stopoperation of the tape. In the wear process metallic particles in theform of a dust come off of the magnetic tape and sometimes find theirway onto the magnetic head or the front side surface of the magnetictape. These dust particles can in these places cause scratching of thetape and errors in the recording of bits of information on the magneticlayer.

It is thus an object of this invention to provide a method and apparatusfor depositing a metallic coating onto one side of a dielectric article.

It is another object of this invention to provide an apparatus for thehigh speed electroplating of a resistive articlewhich is several timesfaster than prior art electroplating apparatuses.

It is another object of this invention to provide an apparatus fordepositing'a uniform electrodeposit onto one conductive surface of acontinuously moving resistive length of article which includes adielectric body having a conductive film thereon, wherein anelectrodeposit thickness may be obtained in one electroplating stagewhich required three or more electroplating stages using prior artapparatuses.

It is a further object of this invention to provide an apparatus for thehigh speed electrodeposition of a magnetic coating onto a continuouslymoving resistive web having uniform and reproducible magneticproperties.

It is a further object of this invention to provide novel, economicaland efiicient methods and apparatuses for electrodepositing a magneticfilm onto a web having a plastic base with a thin conductive coatingthereover for a magnetic recording impulse memory device, which is to beutilized in a very high-speed, high-capacity data processing system.

It is a still further object to provide methods and apparatuses forcontinuously electroplating a magnetic recording tape surface whereinthe plating current density can be precisely controlled with theresultant improvement and reproducibility of the magnetic and physicalproperties of the magnetic coating.

These and other objects are accomplished in accordance with the broadaspects of the present invention by pro viding apparatus for depositingan electrodeposit which includes a cathodic contact which is at leastpartially submerged in the electroplating bath and maintaining theresistive article to be electroplated in tight contact with thesubmerged contact to establish electrical contact between the articleand itself. An electroplating cell is used which contains an appropriateelectroplating solution for depositing the desired metal coating. Theone side of the resistive article is supported in tight contact to thecathodic contact for two purposes. First, to make electrical contactbetween the resistive article and the cathodic contact. The secondpurpose is to seal the electrolyte from between the article and thecontact so that no electroplating can occur on the cathodic contact sideof the article.

The cathodic current path is from the cathodic contact to the conductivefilm on the side of the resistive article pressed against the cathodiccontact, around the conductive film edges of the resistive article andto the opposite side of the article which is not in contact with thecathodic contact. An anode is positioned in the electrolyte. Means areprovided for causing a current to pass between the anode and the cathodeand the resulting electrodeposit is deposited onto only the side of theresistive article which is not in contact with the submerged cathodiccontact means.

The cathodic contact covers a large area of the resistive article andtherefore a large and uniform current can be applied to the article.Since the contact is submerged within the electroplating bath, theelectroplating bath will tend to cool the heat-up of the resistivearticle due to current flow therein. A thick electrodeposit can bedeposited because of the high and uniform current density on theresistive article surface opposite to the cathodic contact. This uniformelectroplating current density improves the magnetic and physicalproperties of the electrodeposit over prior art techniques. Also, asingle electroplating stage can be used to produce the desired coatingproduct thickness. An electrodeposit is deposited on only one side ofthe resistive article because the cathodic contact together with thesupporting means which tightly supports the resistive article againstthe cathodic contact prevents the electrolyte from coming into contactwith the one side of the resistive article. Should it be desired that anelectrodeposit be applied to both sides of the article, theelectrodeposit can readily be applied to one side at a time in theelectroplating apparatus of the present invention.

The foregoing and other objects, features and advantages of the presentinvention will be apparent from the following more particulardescription of the preferred embodiments of the invention as illustratedin the accompanying drawings:

In the drawings:

FIGURE 1 is a schematic illustration of the coating apparatus of thepresent invention;

FIGURE 2 is a perspective view of the electroplating and slittingportions of the FIGURE 1 embodiment of the coating apparatus of thepresent invention;

FIGURE 3 is a schematic illustration of a second embodiment of theelectroplating apparatus portion of the coating apparatus of the presentinvention;

FIGURE 4 is a schematic illustration partially in section, illustratingthe location of the holes in the resistive article in relation to theinsulated and conductive portions of the continuous cathodic beltcontact used in the FIGURE 3 embodiment of the present invention;

FIGURE 5 is a greatly enlarged sectional illustration of the one-sidedelectroplated product of the present invention;

FIGURE 6 is a greatly enlarged sectional illustration of anotherone-sided electroplated product of the present invention; and

FIGURE 7 is a greatly enlarged sectional illustration of a hole portionof the FIGURE 6 product and the holes effect upon the electrodeposit.

Referring now more particularly to FIGURES 1 and 2, there is shown afirst embodiment of the coating apparatus of the present invention. Theapparatus is capable of depositing an electrodeposit onto one side of aresistive article. The invention is illustrated using a continuouslymoving web of resistive material, however, the invention would beequally applicable to a stationary resistive article of material. Adielectric or nonconducting web 10 passes through means 12 for makingholes in the dielectric web. The hole making means 12 can be anyconventional means which preferably allows continuous, rather thanintermittent, movement of the web 10. The dielectric web it) havingholes therein is passed through a conditioning treatment (not shown)where necessary. In the case of a polyethylene terephthalate web aconditioning treatment is necessary to make the surface of the webreceptive to the electroless deposition. The preferred treatment isdescribed in US. patent application Ser. No. 138,609, filed Sept. 18,1961, or Ser. No. 153,187, filed Nov. 17, 1961, both of which areassigned to the assignee of the present invention. The conditioningoperation is not here in described in detail since it is merelyincidental to the present invention. The conditioned web then passesthrough a means 14 for electrolessly depositing a conductive metal film20 onto all exposed surfaces of the dielectric web, including the sidesof the holes in the web. The means 14 for electrolessly depositing theconductive film includes idler rollers 16 for supporting the web on itspath through the electroless plating bath 18 and a drive means 19 forpulling the web through the plating bath at the desired speed.

The electroless plating bath 18 includes chemicals which allow theplating of a conductive metal onto the nonconductive substrate by meansof an autocatalytic chemical reduction reaction. This chemical orelectroless plating process does not depend on the presence of a couplebetween galvanically dissimilar metals. Instead, the mechanism of thereaction is based on a chemical added to the plating solution which actsas a reducing agent for the metal being plated. In electroless plating,the metal ion in solution is reducing to the corresponding metal bygaining the required number of electrons. The source of these electronsis the oxidation of the reducing agent which generally in the art is thehypophosphite ion.

The web 2i) leaving the means 14 for electrolessly depositing aconductive film is resistive in nature. The web 20 shown in magnifiedcross section is resistive because the electrolessly depositedconductive film 21 is so thin. This conductive film Z1 completely coversall exposed surfaces of the dielectric body of the web 10, including thesides of the holes provided in the web by means 12.

The resistive web 20 is then passed into the means 22 forelectrodepositing a metallic layer onto one side of the resistive web.The resistive web is passed around the at least partially submergedconductive member, such as conductive drum 24, within an appropriateelectrolyte 26. Means, such as idler rollers 28 and 30, continuouslyguide the resistive Web 20 around and in tight contact to the conductivedrum 24. A shaped anode 32 having a curvature similar to the conductivedrum 24 and spaced therefrom is positioned in the electrolyte 26. Acurrent source, which is generally illustrated as battery 34 in thedrawing, has its positive side connected to the anode 32 through switch36. The negative side of the current source 34 is connected to theconductive drum 24 by means of a brush 38. The idler roller means 28 and30 guide and support the resistive Web in tight contact with theconductive drum 2 4 to establish electrical contact between theconductive film 20 and the conductive drum 24. Further, this tightcontact effectively seals the electrolyte from between the resistivearticle and the drum.

The drum 24 preferably has continuous insulated surface areas 25 aroundits periphery. The areas 25 are located at the side edges of the drumand Wherever a column of holes in a resistive web passes over the drum,the remaining surface areas of the drum are conductive. These insulatedareas deter electroplating onto the surface of drum 24.

The current path is from the positive terminal of current source 34through the lead to the shaped anode 32 through the electroplating bath26, through the conductive film on the side of the web opposite end tothe submerged conductive member 24. The current path continues throughthe conductive film around the edges of and through the holes in theresistive web to the conductive film on the side of the resistive webadjacent to the cathodic drum '24. The current path proceeds from theconductive film to the cathodic drum contact 24, across the brushcontact 38 and to the negative side of the current source 34.

A large and uniform current density is applied to the conductive film 21of the web 20 by means of the couductive drum 24 because of the largearea of electrical contact between the drum and the conductive film, andthe cooling effect of the bath in reducing resistive heat-up of the web20. The higher current density, in turn, allows a faster electroplatingrate than the prior art external cathodic contact had. The uniformity ofcurrent density produces a vastly superior magnetic coating in physicalcharacteristics, such as smoothness, brightness, hardness, toughness andductility. This is especially advantageous when electroplating an alloybecause current density affects the alloy composition. The variation ofthe alloy along the length of the electrodeposit is, of course, veryundesirable because it affects the magnetic properties along the lengthof the article.

An electrodeposit 41 is deposited onto only one side of the resistiveweb '20 in the electroplating means 22 to produce the metal coated web40', shown in magnified cross section. The Web is pulled through thebath by drive means 42 which is driven in unison with the drive means19. The web 40 is then moved through the slitter means 44 wherein theelectroplated Web is cut along its length to the desired widths.Conveniently, the slitting operation can be used to eliminate all tracesof the holes used in the web for maintaining the uniformity of currentdensity during electroplating. To to this the originally punched holesare positioned along the line through which the slitting means 44 isintended to pass. The holes would thereby be cut out during the slittingoperation. The cut widths of web are then rolled up on spool members 50.

FIGURE 3 illustrates the preferred embodiment of the electrodepositingapparatus for depositing a metallic layer onto one side of a resistiveweb 20. The electroplating means 52 in this embodiment differs from theelectroplating means 22 in the first embodiment principally in the formof the cathodic contact means. The cathodic contact means includescathodic contact rollers 54, a submerged dielectric roller 56 in asuitable electrolyte 58 and a continuous belt 60 composed of aconductive metal. The conductive contact belt 60 is continuously guidedaround the dielectric roller 56 and guides 62, which are preferablycomposed of a polytetrafluoroethylene polymer such as Teflon. It is alsopreferred, although not absolutely necessary, to guide the conductivebelt through a stripping bath 64, followed by a rinsing bath 66. Thestripping bath acts to remove electrodeposits which tend to form on thebelts surfaces. The conductive belt '60 passes through these baths overidler rollers 68 and is moved along its path through the stripping bath,rinsing bath and back to the electroplating apparatus by means of driveroller 70. A shaped anode 72 is provided within the electroplating bath.The shape of the anode is similar to that of the conductive belt 60 asit passes in its prescribed path within the electrolyte 58.

A current source, illustrated as battery 74, has its positive sideconnected through switch 76 to the anode 72. The battery has itsnegative side connected through brush means 78 to the current contactroller 54. The resistive film is guided over the conductive belt bymeans, illustrated as rollers 80 and $2, for continuously guiding itaround and in tight contact to the conductive belt member 60 toestablish electrical contact between the conductive film on the web andeffectively seal the electrolyte from the surface of the belt.

The conductive belt means is preferably constructed of a plurality ofalternate conductive and dielectric belts as illustrated in FIGURE 4when the resistive Web contains holes for increasing the uniformity ofthe electrodeposit. However, a single belt with appropriately positioneddielectric areas could equally serve the purpose of the plurality ofbelts, but would be more difficult to construct. 'In order to counteractthe action of the electrolyte touching the conductive belt through theholes, insulated belts are positioned in the areas where the holes inthe resistive web would strike the belt and at the edges of theresistive web. The belt 66 would then be composed, as shown in FIGURE 4,of dielectric or nonconducting belts 84 and conductive belts 86. Aseries of brushes 78 would contact each of the conductive belts 86 tothereby connect the negative side of the current source '74 to thecathodic contact belt 60.

The purpose of providing holes in the dielectric web prior toelectrolessly depositing a conductive film over the external surface ofthe web can be more readily understood by references to FIGURES 5, 6 and7. The cathodic contact for electroplating onto the conductive film ison one side of the web. The conductivefilm 20 is resistive in nature,therefore the current density will be reduced proportionately as itprogresses from the source of current. The region of highest currentdensity is where the greatest electroplating occurs. This is brought outin FIG- URE 5. At the corners of the web 40 the greatest amount ofelectrodeposit 41 is found and in the center of the electrodeposit onthe web there is found the least amount of electrodeposit. The use ofconductive holes is the novel solution proposed by this invention toremove this nonuniformity of current density which in turn causes anonuniformity of electrodeposit.

FIGURES 6 and 7 show that uniformity of electrodeposit is obtained byuse of conductive holes. The conductive layer 20 covers the entireexternal surface of the dielectric article 10, including the sides ofthe holes. The holes form shortened current paths to the side of theresistive web upon which an electrodeposited layer is deposited. Thecurrent paths around the edges of and through the holes in the resistivearticle allow the uniformity of current density with the improvement inelectrodeposit.

The following examples are included merely to aid in the understandingof the invention, and variations may be made by one skilled in the artwithout departing from the spirit of the invention.

EXAMPLE 1 An elongated, polyethylene terephthalate web was firstconditioned according to the treatment of U.S. patent application Ser.No. 153,187, referred to above, and then was sensitized by successiveexposure to a stannous chloride solution and a palladium chloridesolution with water rinsing after each exposure. The stannous chloridesolution included 30 grams/liter of stannous chloride, 10 milliliters/liter hydrochloric acid and the balance water. The

palladium chloride solution included 0.1 gram/liter palladium chloride,10 milliliters/liter hydrochloric acid and the balance water. Thesensitized web at this time had a thin coating of palladium on itssurface.

The sensitized web was drawn through an electroless plating bath whereina thin film of approximately to micro-inches of metal was deposited ontothe sensitized Current Coer- Remanent Density Time in Web Speed Temp,civity He Magnetiza- Ex. in amps. Bat-h in in feet] 0. Amps. pH in tionin per sq. it. see. min. Oersteds e.m.u.

12 6. 2 53 2. 8 3. 4 750 4 3X10- 6 13. 3 70 5. 5 3. 4 640 5. 5X10- '754% 18. 3 70 8. 2 3. 4 750 5. 0X10- 100 3 25 70 11. O 3. 4 750 5 3X10-150 2 37 7O 16. 5 3. 4 770 4 5X10- surface. The electroless bath had thefollowing composition and operating conditions:

Nickel sulfate hexahydrate (NiSO .6H O) Grams/liter 18.4

Sodium hypophosphite monohydrate The web was drawn from the electrolessplating tank and rinsed with water.

The electroplating set-up included four electroplating cells throughwhich the nickel coated web was drawn. Just prior to the entrance of theresistive nickel coated web into each of the electroplating cells, theweb passed over a cathodic contact roller. Each electroplating cellincluded an electrolyte having the following composition and operatingconditions:

Cobalt sulfate (CoSO .7H O) GramS/liter Nickel sulfate (NiSO .6H O) do40 Sodium hypophosphite (NaH PO I-I O) do 1.0 Ammonium chloride (NH Cl)do Temperature C 53 pH 3.4

The web could be effectively electroplated only a short distance fromthe external cathodic contact roll and the depth of immersion of the webin the electrolyte is adjusted accordingly. The current at the firstelectroplating station was approximately 0.5 to 2.0 amps; at the secondplating station the current was 1 to 3 amps; at the third station thecurrent was 1.5 to 3.5 amps; and the current at the fourth station wasbetween 2.0 and 4.0 amps. The resulting electroplated web had acoercivity of 600 oersteds and an M of 7.0. The web was drawn throughthe electroplating baths at a speed of 10 feet per minute.

EXAMPLES 2, 3, 4, 5 AND 6 Polyethylene terephthalate webs wereconditioned, sensitized and electrolessly plated according to theprocedure of the Example 1. The FIGURE 3 electroplating apparatus wasused except for the stripping and rinsing baths for the conductive belt.The electrolyte composition was as follows:

Cobalt sulfate (CoSO .7H O) Grams/liter 60 Nickel sulfate (NiSO4J6H20)do 40 Sodium hypophosphite (NaH PO .H O) do 1.0 Ammonium chloride (NHcl) do 70 Saccharin do 2 The electrodeposits were on one side of theresistive web. The deposits were bright, smooth and continuous. Thesquareness ratios and coercivities of all examples were good.

The remanent magnetization, M value is a thickness measuring tool forthin magnetic layers. Using the remanent magnetization values as a guidean evaluation of the thickness of the magnetic layer electrodepositedcan be made. The Example 1 apparatus required four electroplatingstations to get up above the minimum value of 5.0 10- e.rn.u. for use asa magnetic record member. Examples 3, 4 and 5 obtained electrodepositshaving M, values of above 5.0x 1O- e.m.u. in a single electroplatingstation using plating speeds of up to 2 /2 times faster speed than theExample 1 apparatus. Examples 2 and 6 were only slightly below theminimum M value.

The invention thus provides an apparatus and a method for substantiallyincreasing the speed of coating a plastic article with a metallic layerover prior methods and apparatuses. Prior art apparatus required threeor four electroplating operations to produce a thickness of metalliccoating on a resistive article equal to what the applicant accomplishesin one electroplating operation with his novel method and apparatus.Further, the speed of electroplating has been increased from two tothree or more times the prior art procedure. Another important advantageof the applicants apparatus over the prior art apparatuses is in theelimination of the drying effect of the electrodeposit as the articlepasses between each electroplating cell. This drying between the cellsproduces a final product which is composed of layers rather than asingle thickness of electroplate. The precisely controlled currentdensities obtained using the techniques of the present invention allowan improvement in the physical prop erties of the electrodeposit.

Any metal capable of being electroplated can be electrodeposited onto ahigh resistive article according to the methods and apparatuses of thisinvention. Alloys of these metals, of course, can be codeposited whensuitable electrolytes known to the art are used. The ferromagneticmetals, iron, nickel and cobalt, have been very successfully codepositedfrom aqueous electrolytes using the techniques of the present invention.

Although the described embodiments presented are onestage electroplatingapparatuses and methods, it is obvious to one skilled in the art thatmore than one electroplating stage can be used. Such a multistageprocess allows the electrodeposit of even thicker total electrodeposits,or an electrodeposition onto each side of the resistive article, ifdesired. Also layers of different metals may thereby be applied one ontop of another.

While the invention as been particularly shown and described withreference to the preferred embodiment thereof, it will be understood bythose skilled in the art that the foregoing and other advantages in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is:

1. Apparatus for depositing an electrodeposit onto one surface of adielectric length of article, including means arranged to guide saidarticle through a plurality of treatment means in sequence, as follows:

means for producing holes through said dielectric length of article;

means for depositing a conductive film onto all exposed surfaces of saiddielectric article having holes therein to form a resistive article; and

means for electrodepositing a metallic layer onto one side of saidarticle, including electroplating cell means adapted to contain anappropriate electrolyte for depositing said metallic layer, electricalcontact means within said cell means over which said reresistive articlemay be guided and supported to establish electrical contact whileforming a fluid tight seal between said contact means and said article,electrode means within said cell means space-d apart from said contactmeans, a current source having a negative side and a positive side,means for connecting the negative side of said current source to saidelectrical contact means and the positive side of said current source tosaid electrode means, thus making the electrical contact means and saidresistive article in electrical contact therewith a cathode and theelectrode means an anode of the electrodepositing means, whereby saidelectrodeposit is deposited onto only the side of said article oppositeto the electrical contact means by virtue of the cathodic current pathestablished through the said conductive film in contact with saidcontact means, around the edges of and through the said holes in saidarticle, and to said opposite side.

2. The apparatus of claim 1 in which the article is a web and in whichthere is means for continuously moving said web through the plurality oftreatment means.

3. The apparatus of claim 2 wherein the holes are made in columns alongthe length of said web and the contact means has non-conductive areaswhere the said holes in the said web are in contact with said contactmeans.

4. The apparatus of claim 1 in which the electrical contact means is adrum and the surface of the electrode means nearest said drum has acurvature similar to said drum.

5. The apparatus of claim 4 by which the resulting plated article is amagnetic recording media having a uniform magnetic electroplatedcoating.

6. The apparatus of claim 3 in which there are means for slitting saidelectroplated web along the column of holes.

7. Apparatus for depositing an electrodeposit onto one surface of adielectric length of article including holes therein, including meansarranged to guide said article through a plurality of treatment means insequence, as follows:

means for depositing a conductive film onto all exposed surfaces of saiddielectric article having holes therein to form a resistive article; and

means for electrodepositing a metallic layer onto one side of saidarticle, including electroplating cell means adapted to contain anappropriate electrolyte for depositing said metallic layer, electricalcontact means within said cell means over which said resistive articlemay be guided and supported to establish electrical contact whileforming a fluid tight seal between said contact means and said article,electrode means within said cell means and spaced apart from saidcontact means, a current source having a negative side and a positiveside, means for connecting the negative side of said current source tosaid electrical contact means and the positive side of said currentsource to said electrode means, thus making the electrical contact meansand said resistive article in electrical contact therewith a cathode andthe electrode means an anode of the electrodepositing means, wherebysaid electrodedeposit is deposited onto only the side of said articleopposite to the electrical contact means by virtue of the cathodiccurrent path established through the said conductive film in contactwith said contact means, around the edges of and through said holes insaid article, and to said opposite sides.

8. Apparatus for depositing an electrodeposit onto one surface of adielectric length of article, including means arranged to guide saidarticle through a plurality of treatment means in sequence, as follows:

means for producing holes through said dielectric length of article;

means for depositing a conductive film onto all exposed surfaces of saiddielectric article having holes therein to form a resistive article; and

means for electrodepositing a metallic layer onto one side of saidarticle, including electroplating cell means adapted to contain anappropriate electrolyte for depositing said metallic layer, strippercontaining means separate from said cell means and adapted to contain astripping bath, a dielectric roller in said cell means, electricalcontact roller means outside of said cell means, a continuous beltcomposed of conductive material continuously guided through said cellmeans around said dielectric roller and in electrical contact with saidcontact roller and through said stripper containing means, a shapedelectrode residing in the cell means and having a curvature similar tothe path of the conductive belt through the cell means and spacedtherefrom, means for continuously guiding said resistive article aroundand in fluid tight electrical contact with said conductive belt memberwithin said cell means, a current source having a negative side and apositive side, means for connecting the negative side of said currentsource to said electrical contact roller and thereby to said conductivebelt member and the positive side of said current source to said shapedelectrode, whereby said electrodeposit is uniformly deposited onto onlythe side of said article opposite to said belt by virtue of the cathodiccurrent path established through the said conductive film in contactwith said belt, around the edges and through the said holes in saidarticle and to said opposite side.

9. The apparatus of claim 8 in which the resulting plated article is amagnetic recording media having a uniform magnetic electroplatedcoating.

10. The apparatus of claim 8 wherein the holes are made in columns andthere are means for slitting the plated article along the columns ofholes.

11. The apparatus of claim 8 wherein the conductive belt has at leastone continuous insulated area around its peripheral length and itsremaining peripheral surfaces being composed of conductive material andthere are guide means for positioning the column of holes in the articleover said insulated portion of the belt.

12. A method for uniformly electroplating a dielectric substratecomprising:

providing holes through the dielectric body;

depositing a conductive film onto all exposed surfaces of said bodyhaving holes therein to produce a resistive substrate;

plalcing said resistive substrate in a suitable electroproviding ananode in said electrolyte;

applying a cathodic contact to one side of said sub" strate;

passing an electroplating current between said anode and said conductivefilm whereby a uniform current density is established on the side of theweb opposite columns, and the plated substrate is slit along the saidcolumn of holes.

14. The method of claim 13 wherein the cathodic contact is a conductivebelt which is continuously moved through the plating solution, adeplating solution, and a rinsing solution to provide a cathodic beltwhich is free of surface impurities at all times.

References Cited UNITED STATES PATENTS 8/1966 Greene et a1 20428 7/1966Polleys et a1. 20428 1 2 2,232,019 2/ 1941 Beckwith 204206 2,019,99411/1935 Rhodes 204-211 2,477,808 8/ 1949 Jones 204211 1,430,855 10/ 1922Schlotter 204209 5 FOREIGN PATENTS 888,495 7/ 1953 Germany. 119,031 4/1930 Germany.

10 OTHER REFERENCES IBM Technical Disclosure Bulletin, volume 6, No. 8,January 1964, page 68.

HOWARD S. WILLIAMS, Primary Examiner. 15 JOHN H. MACK, Examiner.

T. TUFARIELLO, Assistant Examiner.

1. APPARATUS FOR DEPOSITIING AN ELECTRODEPOSIT ONTO ONE SURFACE OF ADIELECTRIC LENGTH OF ARTICLE, INCLUDING MEANS ARRANGED TO GUIDE SAIDARTICLE THROUGH A PLURIALITY OF TREATMENT MEANS IN SEQUENCE AS FOLLOWS:MEANS FOR PRODUCING HOLES THROUGH SAID DIELECTRIC LENGTH OF ARTICLE;MEANS FOR DEPOSITING A CONDUCTIVE FILM ONTO ALL EXPOSED SURFACES OF SAIDDIELECTRIC ARTICLE HAVING THEREIN TO FORM A RESISTIVE ARTICLE; AND MEANSFOR ELECTRODEPOSITING A METALLIC LAYER ONTO ONE SIDE OF SAID ARTICLE,INCLUDING ELECTROPLATING CELL MEANS ADAPTED TO CONTAIN AN APPROPRIATEELECTROLYTE FOR DEPOSITING SAID METALLIC LAYER, ELECTRICAL CONTACT MEANSWITHIN SAID CELL MEANS OVER WHICH SAID RERESISTIVE ARTICLE MAY BE GUIDEDAND SUPPORTED TO ESTABLISH ELECTRICAL CONTACT WHILE FORMING A FLUIDTIGHT SEAL BETWEEN SAID CONTACT MEANS SAID ARTICLE, ELECTRODE MEANSWITHIN SAID CELL MEANS SPACED APART FROM SAID CONTACT MEANS, A CURRENTSOURCE HAVING A NEGATIVE SIDE AND A POSITIVE SIDE, MEANS FOR CONNECTINGTHE NEGATIVE SIDE OF SAID CURRENT SOURCE TO SAID ELECTRICAL CONTACTMEANS AND THE POSITIVE SIDE OF SAID CURRENT SOURCE TO SAID ELECTRODEMEANS, THUS MAKING THE ELECTRICAL CONTACT MEANS AND SAID RESISTIVEARTICLE IN ELECTRICAL CONTACT THEREWITH A CATHODE AND THE ELECTRODEMEANS AN ANODE OF THE ELECTRODEPOSITING MEANS, WHEREBY SAIDELECTRODEPOSIT IS DEPOSITED ONTO ONLY THE SIDE OF SAID ARTICLE OPPOSITETO THE ELECTRICAL CONTACT MEANS BY VIRTURE OF THE CATHODIC CURRENT PATHESTABLISHED THROUGH THE SAID CONDUCTIVE FILM IN CONTACT WITH SAIDCONTACT MEANS, AROUND THE EDGES OF AND THROUGH THE SAID HOLES IN SAIDARTICLE, AND TO SAID OPPOSITE SIDE.